Abstract: Based on the meteorological data and forest investigation data in several regions of Hunan Province during the huge ice disaster from January 13 to February 5,2008,damage degree of the forests was compared and analyzed.It was found that the forests were mechanically damaged by the stems broken,whole tree fell down,or tops and twigs broken.Some tree species also suffered from physiological harm besides mechanical damage.The proportions with intermediately to seriously damaged timber volumes were in a range of 40% to 100% for Pinus massoniana,Pinus elliottii,Cunninghamia laceolata,and the mixed wood of conifer and broadleaf trees in different regions,depended on intensity of the ice disaster.The most serious disaster occurred in the southern regions,such as Chengzhou,Yongzhou,Hengyang and etc.The disaster degree in the north part of Hunan,such as Yiyang,Changde and Yueyang,was relatively light.The other regions of Hunan were recognized as the serious disaster area.The meteorological reasons causing the ice disaster included high average dairy air temperature(-1℃-0℃)that was higher than that occurred during the terms when similar ice disaster happened in the previous years,combined with high average dairy relative humidity(greater than 85%).The weather lasted for many days so that ice crystals formed easily and over developed on the surface of trunks,twigs or electric wires.Those characteristics made this ice disaster different from others recorded ones in the same area.This rare phenomenon may relate to the global warming climate and the density increase of floating dust particles in sizes of nanometers.

Key words: forest, ice disaster, temperature, relative humidity, ice crystal